Semiconductor device and method of fabricating the same

ABSTRACT

There is provided an active matrix type display device in which the display device is formed of a driver circuit with an insulated gate FET capable of operating at high speed, and even if an area of a pixel electrode per unit pixel is made small, sufficient storage capacitance can be obtained. In a semiconductor device comprising an active matrix circuit with an insulated gate field effect transistor having at least an active layer made of single crystalline semiconductor, an organic resin insulating layer is formed over the insulated gate field effect transistor, a storage capacitance is formed of a light shielding layer formed over the organic resin insulating layer, a dielectric layer formed to be in close contact with the light shielding layer, and a light reflecting electrode connected to the insulated gate field effect transistor.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a semiconductor device includingan integrated circuit with an insulated gate field effect transistorhaving an active layer made of single crystalline semiconductor, and amethod of fabricating the same. Particularly, the present invention issuitable for use in an electro-optical device typified by a liquidcrystal display device or electroluminescence (EL) display device inwhich a pixel portion (active matrix circuit) and a driver circuitconnected to the pixel portion are provided on the same substrate, andan electronic equipment incorporating the electro-optical device.Incidentally, in the present specification, the term “semiconductordevice” indicates any devices functioning by using semiconductorcharacteristics, and includes the foregoing electro-optical device andthe electronic equipment incorporating the electro-optical device in itscategory.

[0003] 2. Description of the Related Art

[0004] In a flat plate type display device (flat panel display) typifiedby a liquid crystal display device, an EL display device, or the like,there is known a technique for fabricating an active matrix type displaydevice by using an insulated gate field effect transistor (hereinafter,a field effect transistor is referred to as an “FET”) formed on a singlecrystalline semiconductor substrate. This is different from the casewhere a thin film transistor (hereinafter referred to as a “TFT”) isformed on a glass substrate or quartz substrate and an active matrixtype display device is fabricated, and it is possible to directly applythe technique developed in a large scale integrated circuit (LSI), andthere has been a merit in that high performance FETs operating at highspeed and driven by low voltage can be formed and integrated on asubstrate to a high density. However, on the other hand, it has beenconsidered that the technique has such defects that this is restrictedto a reflection type or spontaneous light emitting type display devicesince the substrate is opaque to visible light, or a single crystallinesemiconductor substrate is limited to a size supplied on the market.

[0005] However, in the technical direction, such as improvement ofpicture quality or full digitization, in a field of a display device,performance improvement required for the active matrix type displaydevice has inevitably become high. In the active matrix type displaydevice, such structure has been adopted that several tens to severalmillion transistors (TFT, FET, etc.) are arranged in a pixel portion forcarrying out picture display, and a pixel electrode is connected to eachof the transistors. Then, the device is constructed such that a voltageapplied to each pixel is controlled by a switching function of thetransistor to drive a liquid crystal or to cause an EL component to emitlight so that a picture is displayed. For example, in the case of aliquid crystal display device, an opposite electrode is provided at theside of an opposite substrate with an intervening liquid crystal, and akind of capacitance (in the present specification, it is referred to as“liquid crystal capacitance”) with the liquid crystal as a dielectric isformed. By controlling the electric charge stored in the liquid crystalcapacitance, the liquid crystal is driven, and the amount of lighttransmitted through the liquid crystal is controlled to display apicture. However, since the capacity of this liquid crystal capacitanceis gradually decreased by a leak current, the amount of transmittedlight is changed and deterioration in the contrast of picture displayhas been caused. Then, it has been necessary to provide anothercapacitor (hereinafter referred to as a “storage capacitance”) differentfrom the liquid crystal capacitance for each pixel. This storagecapacitance functions to compensate capacity which the liquid crystalcapacitance has lost, and is provided to hold the electric charge in aperiod of one frame from writing to next writing. In an EL displaydevice, such construction has been adopted that when a switchingtransistor provided for each pixel is turned on, a current flows to acurrent controlling transistor by a signal corresponding to picturedata, and the EL component spontaneously emits light.

[0006] In such an active matrix type display device, it is expected thata digital system becomes the mainstream in order to realize furtherimprovement in fineness and improvement in density of pictureinformation in the future. For that purpose, it is necessary to newlyprovide a circuit necessary for processing digital signals, such as aDigital/Analog (D/A) converter or a latch circuit, and the structure ofa driver circuit becomes complicated as compared with a conventionalanalog system, and it has been a problem to form a display device by adriver circuit with a transistor capable of operating at high speed.However, in a TFT formed on a glass substrate or quartz substrate, evenif polycrystalline silicon is used for its active layer, an electronmobility to be obtainable is about 400 cm²/V·sec, which is about ⅓ ofthat of an FET fabricated by single crystalline silicon.

[0007] Further, when a pixel density is increased, an area of a pixelelectrode per pixel becomes small, and the ratio of occupation bywirings and transistors inevitably becomes large, so that there has beena problem in that an aperture ratio is lowered. Besides, since an areawhere a storage capacitance can be formed becomes small as the area ofthe pixel electrode is reduced, there has been a problem in that itbecomes difficult to form, with a limited area, a capacitance necessaryfor driving a pixel portion.

SUMMARY OF THE INVENTION

[0008] The present invention has been made to solve the foregoingproblems, and has an object to provide a display device driven by adriver circuit with an insulated gate type FET capable of operating athigh speed, and further, to provide an active matrix type display devicewhich can obtain a sufficient storage capacitance even if an area of apixel electrode per unit pixel is made small. Another object is toprovide an active matrix type liquid crystal display device having lowconsumed electric power and high reliability.

[0009] According to the structure of the present invention, in order tosolve the above problems, there is provided a semiconductor devicecomprising a pixel portion with an insulated gate field effecttransistor having at least an active layer made of single crystallinesemiconductor, characterized in that an organic resin insulating layeris formed over the insulated gate field effect transistor, a storagecapacitance is formed of a light shielding layer formed over the organicresin insulating layer, a dielectric layer formed to be in close contactwith the light shielding layer, and a light reflecting electrodeconnected to the insulated gate field effect transistor.

[0010] According to the structure of the present invention, there isprovided a semiconductor device comprising a pair of substrates and aliquid crystal interposed therebetween, characterized in that aninsulated gate field effect transistor having at least an active layermade of single crystalline semiconductor, an organic resin insulatinglayer formed on the insulated gate field effect transistor, a storagecapacitance is formed of a light shielding layer formed on the organicresin insulating layer, a dielectric layer formed to be in close contactwith the light shielding layer, and a light reflecting electrodeconnected to the insulated gate field effect transistor are formed onone of the substrates, and at least a light transmitting conductive filmis formed on the other of the substrates.

[0011] According to the structure of the present invention, there isprovided a semiconductor device comprising an insulated gate fieldeffect transistor having at least an active layer made of singlecrystalline semiconductor, and an organic EL component, characterized inthat an organic resin insulating layer formed over the insulated gatefield effect transistor, a storage capacitance is formed of a lightshielding layer formed on the organic resin insulating layer, adielectric layer formed to be in close contact with the light shieldinglayer, and a light reflecting electrode connected to the insulated gatefield effect transistor.

[0012] It is preferable in the present invention that an insulatinglayer made of an inorganic compound is formed between the organic resininsulating layer and the light shielding layer, or an insulating layermade of an inorganic compound is formed on a surface of the organicresin insulating layer at a side where the light shielding layer isformed.

[0013] It is desirable in the present invention that the light shieldinglayer is made of at least one kind of material selected from aluminum,tantalum, and titanium, and the dielectric layer is an oxide of thematerial.

[0014] Further, according to the structure of the present invention,there is provided a method of fabricating a semiconductor devicecomprising a pixel portion with an insulated gate field effecttransistor having at least an active layer made of single crystallinesemiconductor, characterized by comprising the steps of: forming anorganic resin layer over the insulated gate field effect transistor;forming a light shielding layer over the organic resin layer; forming adielectric layer to be in close contact with the light shielding layer;and forming a light reflecting electrode including a region overlappingwith the light shielding layer through the insulating layer.

[0015] According to the structure of the present invention, there isprovided a method of fabricating a semiconductor device comprising apair of substrates and a liquid crystal interposed therebetween,characterized by comprising the steps of: forming an insulated gatefield effect transistor having at least an active layer made of singlecrystalline semiconductor over one of the substrates; forming an organicresin layer over the insulated gate field effect transistor; forming alight shielding layer over the organic resin layer; forming a dielectriclayer to be in close contact with the light shielding layer; forming alight reflecting electrode connected to the insulated gate field effecttransistor; and forming a light transmitting conductive film over theother of the substrates.

[0016] According to the structure of the present invention, there isprovided a method of fabricating a semiconductor device comprising aninsulated gate field effect transistor having at least an active layermade of single crystalline semiconductor, and an organic EL component,characterized by comprising the steps of: forming an organic resin layerover the insulated gate field effect transistor; forming a lightshielding layer over the organic resin layer; forming a dielectric layerto be in close contact with the light shielding layer; and forming alight reflecting electrode connected to the insulated gate field effecttransistor.

[0017] It is preferable in the present invention that an insulatinglayer made of an inorganic compound is formed between the organic resininsulating layer and the light shielding layer, or an insulating layermade of an inorganic compound is formed over a surface of the organicresin insulating layer at a side where the light shielding layer isformed.

[0018] It is desirable in the present invention that the light shieldinglayer is made of at least one kind of material selected from aluminum,tantalum, and titanium, and the dielectric layer is an oxide of thematerial. Here, it is desirable that the dielectric layer is formed byan anodic oxidation method.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In the accompanying drawings:

[0020]FIGS. 1A to 1C are sectional views showing fabricating steps of apixel portion and a logic circuit;

[0021]FIGS. 2A to 2C are sectional views showing fabricating steps ofthe pixel portion and the logic circuit;

[0022]FIG. 3 is a sectional view showing a fabricating step of the pixelportion and the logic circuit;

[0023]FIG. 4 is a sectional view of a pixel portion and a logic circuit;

[0024]FIGS. 5A to 5C are sectional views respectively explaining thestructure of a storage capacitance;

[0025]FIG. 6 is a sectional view of an active matrix type liquid crystaldisplay device;

[0026]FIG. 7 is a perspective view of an active matrix type liquidcrystal display device.

[0027]FIG. 8 is a top view of a pixel portion;

[0028]FIG. 9 is a view showing the structure of a projector using areflection type liquid crystal display device;

[0029]FIGS. 10A and 10B are a circuit diagram and a top view of an ELdisplay device, respectively;

[0030]FIG. 11 is a sectional view of an EL display device;

[0031]FIG. 12 is a view showing characteristics between applied voltageand transmissivity in thresholdless antiferroelectric mixed liquidcrystal;

[0032]FIGS. 13A and 13B are control pattern views of forming voltage andforming current, each showing an anodic oxidation method;

[0033]FIG. 14 is a view showing absorbance characteristics of lightshielding films;

[0034]FIGS. 15A and 15B are a view showing a sectional SEM image when anAl film on an organic resin insulating layer has been subjected to ananodic oxidation treatment, and an enlarged schematic view of anelectrode end;

[0035]FIGS. 16A and 16B are a view showing a sectional SEM image when anAl film on an organic resin insulating layer has been subjected to ananodic oxidation treatment, and an enlarged schematic view of anelectrode end;

[0036]FIGS. 17A to 17F are views showing examples of semiconductordevices;

[0037]FIGS. 18A to 18C are sectional views showing fabricating steps ofa pixel portion and a logic circuit;

[0038]FIGS. 19A to 19C are sectional views showing fabricating steps ofthe pixel portion and the logic circuit;

[0039]FIG. 20 is a sectional view showing a fabricating step of thepixel portion and the logic circuit;

[0040]FIG. 21 is a sectional view of an active matrix type EL displaydevice;

[0041]FIGS. 22A and 22B are a top view and a circuit diagram of a pixelportion of an EL display device; and

[0042]FIGS. 23A and 23B are views showing examples of semiconductordevices.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0043] [Embodiment Mode 1]

[0044] An embodiment mode of the present invention will be describedwith reference to FIGS. 1A to 3. Here, a description will be made on anembodiment mode in which a pixel portion and a driver circuit providedat its periphery are provided on the same substrate.

[0045] In FIGS. 1A to 1C, a n-well region 102 and p-well regions 103 and104 were formed in a substrate 101 made of single crystalline siliconhaving comparatively high resistance (for example, n type, about 10 106cm) by one mask in a self-aligning manner. Thereafter, a field oxidefilm 105 was formed. At this time, boron (B) may be selectivelyintroduced into the substrate by an ion implantation method to form achannel stopper. Then, a silicon oxide film 106 which becomes a gateinsulating film was formed by a thermal oxidation method. Subsequently,a polycrystalline silicon film for a gate electrode was formed to athickness of 100 to 300 nm by a CVD method. The polycrystalline siliconfilm for the gate electrode may be previously doped with phosphorus (P)having a concentration of about 10²¹/cm³ in order to lower theresistance, or dense n-type impurities may be diffused after thepolycrystalline silicon film has been formed. Here, in order to furtherlower the resistance, a silicide film having a thickness of 50 to 300 nmwas formed on this polycrystalline silicon film. As a silicide material,it is possible to use molybdenum silicide (MoSix), tungsten silicide(WSix), tantalum silicide (TaSix), titanium silicide (TiSix), or thelike, and the material may be formed in accordance with a conventionalmethod. This polycrystalline silicon film and the silicide film wereetched to form gate electrodes 107 to 109. The gate electrodes 107 to109 have two-layer structure of polycrystalline silicon films 107 a to109 a and silicide films 107 b to 109 b (FIG. 1A).

[0046] Next, in order to form a lightly doped drain (LDD) region in ann-channel FET and a p-channel FET, impurity elements which give ann-type and a p-type conductivity were added using resist masks 110 and113 as masks. Here, phosphorus (P) was ion implanted to the n-channelFET and boron (B) was ion implanted to the p-channel FET. A dose amountwas made 1×10¹³/cm². Here, ion implantation was carried out using thegate electrodes as masks, so that regions 111 and 112 added withphosphorus (P) were formed in regions where the n-channel FETs were tobe formed, and a region 115 added with boron (B) was formed in a regionwhere the p-channel FET was to be formed in a self-aligning manner(FIGS. 1B and 1c).

[0047] Thereafter, an insulating film such as a silicon oxide film or asilicon nitride film was formed on the whole surface by a CVD method,and when this film was uniformly etched over the whole surface byanisotropic dry etching, as shown in FIG. 2A, the insulating filmremained at sides of the gate electrodes, and side walls 116 to 118 wereformed. The side walls were used as masks, and arsenic having a doseamount of 5×10¹⁵/cm² was ion implanted to the regions of the n-channelFETs, so that n-type impurity regions (source or drain regions) 120 and121 were formed. Moreover, as shown in FIG. 2B, boron (B) was ionimplanted to the region of the p-channel FET, so that a p-type impurityregion (source or drain region) 124 was formed using a resist mask 122as a mask.

[0048] Then, the silicon oxide films remaining on the n-type impurityregions (source or drain regions) 120 and 121 and the p-type impurityregion (source or drain region) 124 were removed by etching, and aninterlayer insulating film 125 was formed on the whole surface. Further,a leveling film 126 of phosphorus glass (PSG), boron glass (BSG), orboron phosphorus glass (BPSG) was formed on top of the film 125.Thereafter, in order to activate the ion implanted impurity element, aheat treatment was carried out at 700 to 900° C. The leveling film 126was subjected to reflow by this heat treatment, and the surface wasfurther flattened (FIG. 2C).

[0049] Then, contact holes reaching the n-type impurity regions (sourceor drain regions) 120 and 121 and the p-type impurity region (source ordrain region) 124 were formed in the interlayer insulating film 125 andthe leveling film 126, and source wirings 127, 129, and 131 (connectedto source region 145) and drain wirings 128, 130, and 132 (connected todrain region 146) were formed (FIG. 3). Although a material used forwiring is not limited, it is preferable that aluminum (Al) normally usedas a low resistance material is used. Besides, a laminate structure ofAl and titanium (Ti) may be used.

[0050] In this state, when a heat treatment at 300 to 500° C.,preferably 350 to 450° C. was carried out in an atmosphere containinghydrogen, it was possible to bring characteristics of FETs into a moreexcellent state.

[0051] A passivation film 133 to be formed thereon was formed of asilicon nitride film, a silicon oxide film, or a silicon oxynitride filmby a plasma CVD method. Moreover, an organic resin insulating film 134was formed to a thickness of 1 to 2 μm. As the organic resin material,it was possible to use polyimide, polyamide, acryl, benzo-cyclo-butene(BCB) or the like. The advantages of using the organic resin film aresuch that a method of forming the film is simple, parasitic capacitancecan be reduced since specific dielectric constant is low, and the filmis suitable for flattening. Of course, an organic resin film other thanthe above may be used. Here, polyimide of a type that thermalpolymerization was made after application to the substrate was used, andwas formed through heating to 300° C. in a clean oven and burning.

[0052] Moreover, a light shielding film 135 was formed on this organicresin insulating film 134. The light shielding film 135 was formed of afilm containing an element selected from aluminum (Al), titanium (Ti),and tantalum (Ta). In order to form a storage capacitance with the lightshielding film as one electrode and pixel electrodes 139, which isconnected to drain wiring 132 at a contact hole 147 through openings 137and 138, as the other electrode in the pixel portion, a dielectric layer136 was formed on the light shielding film 135. Although this dielectriclayer can be formed using a silicon oxide film, a silicon nitride film,a silicon oxynitride film, a DLC (Diamond like carbon) film, or theforegoing polyimide film, each film being formed through deposition by aconventional film formation method, it is also possible to form thelayer such that an oxide layer of the light shielding film is formed byusing an anodic oxidation method and this is used as the dielectriclayer 136.

[0053] In the anodic oxidation method, a voltage was applied in anelectrolytic solution (for example, ethylene glycol solution containing3 wt % of tartaric acid) while the light shielding film was used as ananode and platinum was used as a cathode, so that it was possible toform the dielectric layer which is dense and has no pinhole. Althoughthe thickness of the dielectric layer may be 10 to 100 nm for thepurpose of forming the storage capacitance, preferably 20 to 70 nm,since the thickness of the light shielding film is decreased as thedielectric layer is formed, it is important to secure the thickness ofthe light shielding film in view of the decrease.

[0054] Table 1 shows a change in film thickness when an aluminum oxidefilm having a thickness of 50 nm was formed by anodic oxidation of asurface of an Al film, and a value of absorbance to light with awavelength of 550 nm. The absorbance was measured by a spectrophotometer(made by Hitachi, Ltd., type U-4000). TABLE 1 Start Thickness Total filmthick- of Al film Thickness thickness ness of after anodic of Al afteranodic Al film oxidation oxide film oxidation Absorbance Sample (nm)(nm) (nm) (nm) (at 550 nm) A 65 30 50 80 2.6 B 95 60 50 110 4.0 C 125 9050 140 4.6

[0055] For example, when the initial thickness of the Al film was 65 nm,and the aluminum oxide film with a thickness of 50 nm was formed,although the total film thickness was increased to 80 nm, the thicknessof the Al film was decreased to 30 nm. At this time, the absorbance tolight of a wavelength of 550 nm was 2.6. In the samples of Table 1,characteristics of the absorbance to each wavelength are shown in FIG.14. From the data of FIG. 14, it has become apparent that the absorbancedepends on the thickness of the Al film in a wavelength range of between300 and 600 nm. Consequently, from the result of FIG. 14 and visualobservation, it was possible to judge that satisfactory characteristicswere obtainable if the film thickness necessary as the light shieldingfilm was made 60 nm or more, and the absorbance was made 3.0 or more.

[0056]FIGS. 13A and 13B respectively show, in the anodic oxidationmethod, a control pattern of voltage (formation voltage) applied betweenan anode and a cathode, and current (formation current) flowing betweenthe electrodes. In FIG. 13A, the formation current is first controlledto hold a constant value (constant current mode), and voltage is raisedto a voltage value corresponding to a produced film thickness of adielectric layer previously examined. After the voltage value reachesthe predetermined value, the voltage value is held (constant voltagemode). When it was judged that the reaction of the anodic oxidation wasended when the current flowing between the electrodes became a certainset value or less, it was possible to form dielectric layers havingcomparable thicknesses with good reproducibility.

[0057] However, in the control pattern of FIG. 13A, in the case wherethe dielectric layer was formed on the surface of the light shieldingfilm formed on the organic resin insulating film, the electrolyticsolution soaked into the organic resin insulating film so that the filmwas expanded, and further, the electrolytic solution soaked also intothe interface between the light shielding film and the organic resininsulating film, so that the dielectric layer was formed also at theside of the organic resin insulating film as the under layer over thelength of several μm from the end of the light shielding film. Anexample of this state is shown in FIGS. 15A and 15B. FIG. 15A shows aresult of observation, by a scanning electron microscope (S EM), of asectional structure obtained when the Al film formed on the organicresin insulating film was subjected to the anodic oxidation treatmentwith the control pattern of FIG. 13A. FIG. 15B is a schematic viewthereof. In the drawings, providing that the thickness of the dielectricat the end is Xb, and the length of the dielectric formed at the side ofthe organic resin insulating film as the under layer is Xa, a soakingamount X can be defined as a difference between Xa and Xb. According tothe result of FIG. 15A, the soaking amount X was about 2 μm. As aresult, the flatness of the light shielding film was damaged.

[0058] On the other hand, like the control pattern of formation voltageand formation current shown in FIG. 13B, as the constant current mode,the current density was raised 1.2 to 3 times as high as the conditionof FIG. 13A, and after the voltage was rapidly raised in a short time upto a predetermined voltage corresponding to the film thickness of thedielectric layer to be formed on the surface of the light shieldingfilm, the anodic oxidation was ended without holding the voltage or withthe holding time made a very short time, so that it was possible to formthe dielectric layer in which soaking did not occur on the organic resininsulating film. FIG. 16A is a SEM photograph of a light shielding filmon an organic resin insulating film and a dielectric layer formed on thesurface, which was fabricated by the foregoing method. It was possibleto realize the excellent shape in which soaking from the end hardlyoccurred. FIG. 16B is a schematic view thereof. Even when the anodicoxidation was carried out with the control pattern as shown in FIG. 13B,it was possible to form the dielectric film which was dense, had nopinhole, and had high insulation withstand voltage.

[0059] Table 2 shows results of evaluation of soaking amounts from theends of light shielding films when the films were formed under variousanodic oxidation conditions. It was recognized that the soaking amountfrom the end relates to the rising time of voltage and holding time ofvoltage, and it was possible to decrease the soaking amount by makingthe rising time of voltage shorter, and by shortening the constantvoltage time to shorten the total anodic oxidation time. TABLE 2 Rate ofConstant Anodic Current voltage Rising voltage oxidation Soaking Voltagevalue rising time time time amount (V) (mA/sheet) (V/min) (sec) (min)(sec) (Mm) 1 35 1 0.5 to 0.6 3765 0 3765 1 to 2 2 35 20 13.8 122 0 1220.5  3 35 100  87 to 430 7 0 7   0 to 0.05 4 35 20 13.8 128 15 128 0.625

[0060] Here, the pixel electrode 139 was formed, a part of whichoverlapped with the light shielding film through the dielectric layerfabricated by the anodic oxidation method with the control pattern shownin FIG. 13B. This pixel electrode 139 is connected to a drain wiring ofan n-channel FET 143. The pixel electrode was made of a light reflectivematerial typified by Al to form a reflection type display device.

[0061] Although Al can be easily formed by a conventional film formationmethod for example, a vacuum evaporation method or sputtering method, inthe case where the reflection type liquid crystal display device isformed, the surface of the pixel electrode may be roughened to form adiffusing reflection surface so as to improve the contrast.

[0062] In the manner described above, an active matrix substrate wasfabricated in which a driver circuit including, as a base, a CMOScircuit composed of a p-channel FET 141 and an n-channel FET 142, and apixel portion including the n-channel FET 143 and a storage capacitance144 were formed on the same substrate. With respect to the drivercircuit including the CMOS circuit as the base, for example, a shiftregister circuit, a buffer circuit, a sampling circuit, a D/A converter,a latch circuit, or the like can be formed by using the CMOS circuit asthe base. When such a circuit was constructed by an insulated gate FETincluding an active layer made of single crystalline silicon, it waspossible to perform high speed operation, and it was also possible toreduce the consumed electric power by making the driving voltage 3 to 5V.

[0063] In the pixel portion like this, by forming the storagecapacitance with the dielectric film formed to be in close contact withthe surface of the light shielding film, even if the area of the pixelelectrode per pixel was made small, it was possible to form sufficientcapacitance. For example, even if the area of one pixel was made 400μm², it was possible to form a capacitance of about 0.5 pF.

[0064] The structure of the transistor explained in this embodiment modeis merely one embodiment mode, and the present invention is notnecessarily limited to the fabricating steps and the structure shown inFIGS. 1A to 3. The important point of the present invention is thestructure of the FET formed on the single crystalline substrate and thestorage capacitance formed thereon through the organic resin layer.

[0065] [Embodiment Mode 2]

[0066] As an SOI substrate in which a single crystalline silicon layer(SOI: Silicon On Insulators) is formed on an insulator, an active matrixsubstrate can be formed similarly to the embodiment mode 1. With respectto the SOI substrate, although some kinds are known according to thestructure and fabricating method, typically, SIMOX (Separation byImplanted Oxygen), ELTRAN (Epitaxial Layer Transfer: registeredtrademark of Canon K.K.), SmartCut (registered trademark of SOITECInc.), or the like can be used. Of course, other SOI substrates can alsobe used.

[0067]FIG. 4 shows the structure fabricated by using such an SOIsubstrate. The fabricating method may be the same as the embodiment mode1, and it is possible to form a driver circuit including a p-channel FET438 and an n-channel FET 439 and a pixel portion including an n-channelFET 440 and a storage capacitance 441 on a substrate 401 through aninsulating layer 402. The respective FETs are separated by a fieldinsulating film 403.

[0068] The p-channel FET 438 of the driver circuit is provided with agate electrode 407, a side wall 410, a gate insulating film 404, an LDDregion 413, a source region 414 a drain region 415, a source wiring 424,and a drain wiring 425. The n-channel FET 439 is provided with a gateelectrode 408, a side wall 411, a gate insulating film 405, an LDDregion 416, a source region 417; a drain region 418, a source wiring426, and a drain wiring 427. The n-channel FET 440 of the pixel portionis provided with a gate electrode 409, a side wall 412, a gateinsulating film 406, an LDD region 419, a source region 420, a drainregion 421, a source wiring 428, and a drain wiring 429.

[0069] An interlayer insulating film 422 is formed of a silicon oxidefilm, a silicon nitride film, a silicon oxynitride film, or the like,and a leveling film 423 made of PSG, BSG, or BPSG is formed thereon. Apassivation film 430 is made of silicon nitride or silicon oxynitride,and is formed to cover the leveling film 423, the source wirings 424,426, and 428, and the drain wirings 425, 427, and 429. An organic resininsulating film 431 is formed thereon. A light shielding film 432 wasformed of a film containing an element selected from aluminum (Al),titanium (Ti), and tantalum (Ta) as its main ingredient. For the purposeof forming a storage capacitance using this light shielding film 432 asone electrode, a dielectric layer 433 having a thickness of 10 to 100nm, preferably 20 to 70 nm was formed on the light shielding film. Asthe dielectric layer, it is desirable to use a dielectric layer formedon the surface of the light shielding film by using the anodic oxidationmethod. A pixel electrode 436 connected to the drain wiring 429 of then-channel FET 440 through openings 434 and 435 was formed on the lightshielding film 432 through the insulating film 433. Here, in order toform a reflection type display device, the electrode was formed of alight reflective material typified by Al.

[0070] In the manner as described above, on the SOI substrate, it waspossible to form the driver circuit including, as the base, the CMOScircuit composed of the p-channel transistor 438 and the n-channeltransistor 439, and the pixel portion including the n-channel transistor440 and the storage capacitance 441 on the same substrate. With respectto the driver circuit including the CMOS circuit as the base, forexample, a shift register circuit, a buffer circuit, a sampling circuit,a D/A converter, a latch circuit, or the like can be formed by using theCMOS circuit as the base.

[0071] [Embodiment Mode 3]

[0072]FIGS. 5A to 5C show other structural examples of connectionmethods of a storage capacitance provided in a pixel portion. FIGS. 5Ato 5C respectively show a sectional structure of the pixel portionfabricated in the same manner as the embodiment mode 1. In FIG. 5A, apassivation film 503 and an interlayer insulating film 504 made oforganic resin are formed on an n-channel FET 501, and a film 505 made ofinorganic material is formed thereon. This film may be formed by using asilicon oxide film, a silicon nitride film, a silicon oxynitride film,or the like, and may be preferably formed by a sputtering method orvacuum evaporation method. A light shielding film 506 is formed thereon,and adhesion to an under layer is improved, so that even if a dielectriclayer 507 is formed by the anodic oxidation method, soaking of anelectrolytic solution does not occur, and an excellent shape can beformed. By forming a pixel electrode 510 connected to a drain electrode502 through openings 508 and 509 provided in the passivation film 503and the organic resin insulating film 504, a storage capacitance 536 isformed in the region where the pixel electrode 510 overlaps with thelight shielding film 506.

[0073] In FIG. 5B, a storage capacitance 537 connected to an n-channelFET 512 is constituted by a light shielding film 516 formed on anorganic resin insulating film 515, a dielectric layer 517 formed thereonby the anodic oxidation method, and a pixel electrode 522. A spacer 518of insulator is provided in a region where an opening of the organicresin insulating film 515 is formed, and the pixel electrode 522 isconnected to a drain wiring 513 through an opening 519 provided in thepassivation film 514, an opening 520 provided in the organic resininsulating film 515, and an opening 521 provided in the spacer 518. Byproviding the spacer 518 like this, a short circuit occurring betweenthe light shielding film and the pixel electrode can be preventedwithout fail. The storage capacitance 537 is formed in the region wherethe light shielding film 516, the dielectric layer 517, and the pixelelectrode 522 overlap with one another.

[0074]FIG. 5C shows another structure of a storage capacitance 538connected to an n-channel FET 524. A light shielding film 528 and aspacer 529 made of organic resin are formed on an organic resininsulating film 527. A dielectric layer 530 is formed on the surface ofthe light shielding film 528 by the anodic oxidation method. A pixelelectrode 534 is connected to a drain wiring 525 through an opening 531provided in a passivation film 526, an opening 532 provided in theorganic resin insulating film 527, and an opening 533 provided in thespacer 529. The storage capacitance 538 is formed in the region wherethe light shielding film 528, the dielectric layer 530, and the pixelelectrodes 534, 535 overlap with one another. By making such structure,it is possible to form an anodic oxidation film without soaking even onthe organic resin film.

[0075] Next, preferred embodiments of the present invention will bedescribed in detail.

[0076] [Embodiment 1]

[0077] In this embodiment, steps of fabricating an active matrix typeliquid crystal display device from an active matrix substrate fabricatedin the embodiment mode 1 will be described. As shown in FIG. 6, analignment film 601 is formed to the substrate of the state of FIG. 3.Normally, polyimide resin is often used for an alignment film of aliquid crystal display device. A transparent conductive film 603 and analignment film 604 were formed on an opposite side substrate 602. Afterthe alignment film was formed, a rubbing treatment was carried out sothat liquid crystal molecules were oriented in parallel with a specificpre-tilt angle. The active matrix substrate in which the pixel portionand the CMOS circuit were formed, and the opposite substrate were bondedto each other by a conventional cell assembling step through a sealingmaterial, a spacer (neither of them is shown), or the like. Thereafter,a liquid crystal material 605 was injected between both the substrates,and complete sealing was made by a sealing agent (not shown).

[0078] In the liquid crystal display device fabricated in the aboveembodiment, other than a TN (Twisted Nematic) liquid crystal, variousliquid crystals may be used. For example, it is possible to use a liquidcrystal disclosed in 1998 SID, “Characteristics and Driving Scheme ofPolymer-Stabilized Monostable-FLCD Exhibiting Fast Response Time andHigh Contrast Ratio with Gray-Scale Capability” by H. Furue et al.;1997, SID DIGEST, 841, “A Full-Color Thresholdless Antiferroelectric LCDExhibiting Wide Viewing Angle with Fast Response Time” by T. Yoshida etal.; 1996, J. Mater. Chem. 6(4), 671-673, “Thresholdlessantiferroelectricity in liquid crystals and its application to displays”by S. Inui et al.; or U.S. Pat. No. 5,594,569.

[0079] A liquid crystal exhibiting antiferroelectricity in sometemperature range is called an antiferroelectric liquid crystal. Inmixed liquid crystals including antiferroelectric liquid crystals, thereis a thresholdless antiferroelectric mixed liquid crystal exhibitingelectro-optical response characteristics in which transmittance iscontinuously changed with respect to an electric field. Somethresholdless antiferroelectric mixed liquid crystal exhibits V-shapedelectro-optical response characteristics, and a liquid crystal in whichits driving voltage is about +2.5 V (cell thickness is about 1 to 2 μm)has also been found.

[0080] Here, FIG. 12 shows an example of characteristics of lighttransmittance of the thresholdless antiferroelectric mixed liquidcrystal showing the V-shaped electro-optical response to appliedvoltage. The vertical axis of the graph shown in FIG. 12 indicates thetransmissivity (in arbitrary unit) and the horizontal axis indicates theapplied voltage. Incidentally, the transmission axis of a polarizingplate of a liquid crystal display device at an incident side is setalmost parallel to a normal direction of a smectic layer of thethresholdless antiferroelectric mixed liquid crystal which is almostcoincident with the rubbing direction of the liquid crystal displaydevice. The transmission axis of the polarizing plate at an outgoingside is set almost normal (crossed Nicols) to the transmission axis ofthe polarizing plate at the incident side.

[0081] As shown in FIG. 12, it is understood that when such athresholdless antiferroelectric mixed liquid crystal is used, lowvoltage driving and gradation display become possible.

[0082] In the case where such a low voltage driving thresholdlessantiferroelectric mixed liquid crystal is used for a liquid crystaldisplay device having an analog driver, it becomes possible to suppressthe power supply voltage of a sampling circuit of an image signal to forexample, about 5 to 8V. Thus, the operation power supply voltage of thedriver can be lowered, and low power consumption and high reliability ofthe liquid crystal display device can be realized.

[0083] Also in the case where such a low voltage driving thresholdlessantiferroelectric mixed liquid crystal is used for a liquid crystaldisplay device having a digital driver, an output voltage of a D/Aconversion circuit can be lowered, so that the operation power supplyvoltage of the D/A conversion circuit can be lowered and the operationpower supply voltage of the driver can be made low. Thus, low powerconsumption and high reliability of the liquid crystal display devicecan be realized.

[0084] Thus, to use such a low voltage driving thresholdlessantiferroelectric mixed liquid crystal is effective also in the casewhere a TFT having an LDD region (lightly doped drain region) with arelatively small width (for example, 0 to 500 nm or 0 to 200 nm) isused.

[0085] Besides, in general, the thresholdless antiferroelectric mixedliquid crystal has large spontaneous polarization, and the dielectricconstant of the liquid crystal itself is high. Thus, in the case wherethe thresholdless antiferroelectric mixed liquid crystal is used for aliquid crystal display device, it becomes necessary to providerelatively large storage capacitance for a pixel. Thus, it is preferableto use the thresholdless antiferroelectric mixed liquid crystal havingsmall spontaneous polarization. Besides, it is also permissible todesign such that a driving method of the liquid crystal display deviceis made linear sequential driving, so that a writing period (pixel feedperiod) of a gradation voltage to a pixel is prolonged and small storagecapacitance is compensated.

[0086] Since low voltage driving can be realized by using such athresholdless antiferroelectric mixed liquid crystal, low powerconsumption can be realized when the liquid crystal display device isformed by the active matrix substrate of the present invention.

[0087] Incidentally, as long as a liquid crystal has electro-opticalcharacteristics as shown in FIG. 12, any liquid crystal can be used as adisplay medium of a liquid crystal display device of the presentinvention.

[0088] Next, the structure of this active matrix type liquid crystaldisplay device will be described with reference to a perspective view ofFIG. 7 and a top view of FIG. 8. Incidentally, in order to establish thecorrespondence with the sectional structural views of FIGS. 1A to 3 andFIG. 6, common reference numerals to the foregoing drawings are used inFIGS. 7 and 8. An active matrix substrate is constituted by a pixelportion 701 a scanning (gate) line driver circuit 702, and a signal(source) line driver circuit 703 formed on a substrate 101. An n-channeltransistor 143 of the pixel portion, and the driver circuits provided onthe periphery are respectively constructed by a CMOS circuit as a base.The scanning (gate) line driver circuit 702 and the signal (source) linedriver circuit 703 are respectively connected to the pixel portion 701through a gate wiring 109 and a source wiring 131. An FPC 731 isconnected to an external input/output terminal 734. The substrate 101 isfixed to a base plate 736 through a resin layer 735, so that themechanical strength is held, and further, the base plate 736 is made ofa material having excellent thermal conductivity, so that a heatradiation effect can also be obtained.

[0089]FIG. 8 is a top view showing a part of the pixel portion 701. Thegate electrode 109 is formed on single crystalline silicon through agateinsulating film (not-shown). Although not shown, a source region and adrain region are formed in the single crystalline silicon. A lightshielding film 135, a dielectric layer (not shown), and a pixelelectrode 139 provided for each pixel are formed thereon, and a storagecapacitance 143 is formed in the region where the light shielding film135 overlaps with the pixel electrode 139 through the dielectric layer.Since the dielectric layer is made a dielectric film for forming thecapacitance portion, it is possible to reduce an area for formingnecessary capacitance. Further, when the light shielding film formed onthe pixel TFT was made one of electrodes of the storage capacitance asin this embodiment, it was possible to improve an aperture ratio of apicture display portion of the active matrix type liquid crystal displaydevice. Incidentally, a sectional structure along the line A-A′ shown inFIG. 8 corresponds to a sectional view along the line A-A′ of the pixelportion shown in FIG. 3.

[0090] The reflection type liquid crystal display device fabricated inthis way can be used for an electro-optical device of a projection typedisplay device, in addition to an electro-optical device of a directviewing type display device.

[0091] [Embodiment 2]

[0092] In this embodiment, a description will be made on an example ofan electro-optical device in which the present invention is used as adisplay device. A case where a reflection type display device shown inthe embodiment 1 is applied to a three-plate type projection device willbe described with reference to FIG. 9.

[0093] In FIG. 9, light emitted from a light source 901 made of a metalhalide lamp, a halogen lamp, or the like is reflected by a polarizationbeam splitter 902, and advances to a cross dichroic mirror 903.Incidentally, the polarization beam splitter is an optical filter havinga function of reflecting or transmitting light according to thepolarization direction of the light. In this case, light from the lightsource 901 is given such polarization that the light is reflected by thepolarization beam splitter 902.

[0094] At this time, at the cross dichroic mirror 903, a red (R)component light is reflected in the direction of a liquid crystaldisplay device 904 corresponding to red (R), and a blue (B) componentlight is reflected in the direction of a liquid crystal display device906 corresponding to blue (B). A green (G) component light istransmitted through the cross dichroic mirror 903, and is incident on aliquid crystal display device 905 corresponding to green (G). In theliquid crystal display devices 904 to 906 corresponding to therespective colors, liquid crystal molecules are oriented so that whenthe pixel is in an off state, the polarization direction of incidentlight is not changed and the light is reflected. Besides, the devicesare structured such that when the pixel is in an on state, theorientation state of a liquid crystal layer is changed, and thepolarization direction of incident light is also changed in accordancewith that.

[0095] Lights reflected by these liquid crystal display devices 904 to906 are again reflected (green (G) component light is transmitted) bythe cross dichroic mirror 903 and are synthesized, and are againincident on the polarization beam splitter 902. At this time, since thepolarization direction of the light reflected by a pixel region being inthe on state is changed, the light is transmitted through thepolarization beam splitter 902. On the other hand, since thepolarization direction of the light reflected by a pixel region being inthe off state is not changed, the light is reflected by the polarizationbeam splitter 902. Like this, by making on/off control of the pixelregions arranged in a matrix form in the pixel portion through aplurality of transistors, only light reflected by a specified pixelregion becomes possible to be transmitted through the polarization beamsplitter 902. This operation is common to the respective liquid crystaldisplay devices 904 to 906.

[0096] The light transmitted through the polarization beam splitter 902in the manner described above and including image information isprojected onto a screen 908 by an optical lens 907 constructed byprojection lenses or the like. Here, although the basic structure isshown, a projection type electro-optical device can be realized byapplying such a principle.

[0097] [Embodiment 3]

[0098] In this embodiment, an example in which the present invention isapplied to an active matrix type EL display device will be describedwith reference to FIGS. 10A and 10B and FIG. 11. FIG. 10A is a circuitdiagram of the active matrix type EL display device. This EL displaydevice is constituted by a display region 11, an X-direction peripheraldriver circuit 12 and a Y-direction peripheral driver circuit 13provided on a substrate. This display region 11 is constituted by aswitching transistor 330, a storage capacitance 332, a currentcontrolling transistor 331, an organic EL component 333, X-directionsignal lines 18 a and 18 bpower supply lines 19 a and 19 b, Y-directionsignal lines 20 a, 20 b, and 20 c, and the like.

[0099]FIG. 10B is a top view of almost one pixel. A sectional structurealong the line B-B′ in the drawing is shown in FIG. 11. In the sectionalstructure shown in FIG. 11, although a structural example using a singlecrystalline silicon substrate is shown, such a structure can be realizedin the same way even if an SOI substrate is used. An n-well region 302and a p-well region 303 are formed in a substrate 301, and a field oxidefilm 304 is formed to separate adjacent FETs. The switching FET 330 isformed of a p-channel FET, and includes a gate insulating film 305, agate electrode 307, a side wall 309, an LDD region 311, a source region312, a drain region 313, a source wiring 318, and a drain wiring 319.The current controlling transistor 331 is an n-channel FET, and includesa gate insulating film 306, a gate electrode 308, a side wall 310, anLDD region 314, a source region 315, a drain region 316, a source wiring320, and a drain wiring 321. The storage capacitance 332 is formed on aninterlayer insulating film 322, and is formed of a capacitance electrode323 connected to the drain wiring 319 of the switching FET 330, a powersupply line 19 a, and a dielectric layer 324 provided therebetween.Here, when the capacitance electrode 323 is formed of a materialcontaining an element selected from Al, Ta and Ti as its mainingredient, and the dielectric layer 324 is formed by anodic oxidationof its surface, an excellent storage capacitance can be formed. Theorganic EL component 333 is formed through an interlayer insulating film326, and is formed of an EL component lower electrode 327 connected tothe drain wiring 321 of the current controlling FET 331, an organic ELlayer 328, and an EL component upper electrode 329.

[0100] Here, although the structure of the pixel region of the ELdisplay device is shown, similarly to the embodiment 1, it is alsopossible to form an active matrix type display device of a peripheralcircuit integration type in which a driver circuit is provided on theperiphery of the pixel region. Besides, although not shown, when a colorfilter is provided, color display can also be made.

[0101] [Embodiment 4]

[0102] In this embodiment, a description will be given on asemiconductor device incorporating an active matrix liquid crystaldisplay device made from a TFT circuit of the present invention, withreference to FIGS. 17A to 17F and FIGS. 23A and 23B. In thesemiconductor device shown in FIGS. 17A to 17F and FIGS. 23A and 23B, anactive matrix liquid crystal display device shown in the embodiment modeand embodiment of the present invention can be preferably employed.

[0103] As such a semiconductor device, a portable information terminal(an electronic book, a mobile computer, a cellular phone and the like),a video camera, a digital still-image camera, a personal computer, TVetc. may be enumerated. Examples of those are shown in FIGS. 17A to 17F.

[0104]FIG. 17A is a cellular phone that is composed of a main body 9001,a sound output section 9002, a sound input section 9003, a displaydevice 9004, operation switches 9005 and an antenna 9006. The presentinvention can be applied to the sound output section 900′, the soundinput section 9003 and the display device 9004 having a pixel section.

[0105]FIG. 17B shows a video camera that is comprised of a main body9101, a display device 9102, a voice input unit 9103, operation switches9104, a battery 9105, and an image receiving unit 9106. The presentinvention is applicable to the voice input unit 9103, the display device9102 having a pixel section and the image receiving unit 9106.

[0106]FIG. 17C shows a mobile computer that is comprised of a main body9201, a camera unit 9202, an image receiving unit 9203, operationswitches 9204, and a display device 9205. The present invention can beapplied to the image receiving unit 9203 and the display device 9205having a pixel section.

[0107]FIG. 17D shows a goggle type display that is comprised of a mainbody 9301, a display device 9302 and arm portions 9303. The presentinvention can be applied to the display device 9302. Further, althoughnot shown, the present invention can also be used for other signalcontrol circuits.

[0108]FIG. 17E shows a rear-type projector comprising a main body 9401,an optical source 9402, a display device 9403, a polarization beamsplitter 9404, reflectors 9405 and 9406 and a screen 9407. The presentinvention is applicable to the display device 9403.

[0109]FIG. 17F shows a portable electronic book that is comprised of amain body 9501, display device 9503, a memory medium 9504, an operationswitch 9505 and an antenna 9506. The book is used to display data storedin a mini-disk or a DVD, or a data received with the antenna. Thedisplay device 9503 are direct-vision type display devices, to which thepresent invention may be applied.

[0110]FIG. 23A shows a player that employs a recording medium in whichprograms are recorded (hereinafter referred to as recording medium), andcomprises a main body 9701 a display device 9702, a speaker unit 9703, arecording medium 9704, and an operation switch 9705. Incidentally, thisplayer uses as the recording medium a DVD (Digital Versatile Disc), CDand the like to appreciate music and films, play games, and connect tothe Internet. The liquid crystal display device and EL display devicemanufactured by employing the present invention is applicable to thedisplay device 9702.

[0111]FIG. 23B shows a digital camera comprising a main body 9801, adisplay device 9802, an eye piece section 9803, operation switches 9804,and an image receiving unit (not shown). The liquid crystal displaydevice and EL display device manufactured by employing the presentinvention is applicable to the display device 9802.

[0112] Other than those, though not shown here, the present inventionmay be applied to a display section of a navigation system for vehicle,an image sensor and personal computer. The present invention thus has sowide application range that it is applicable to electronic equipment inany field.

[0113] [Embodiment 5]

[0114] In an active matrix type display device using a singlecrystalline semiconductor substrate, since a manufacturing technique ofan integrated circuit, such as LSI or VLSI can be directly applied, asmall-sized display device with high fineness can be fabricated. Forexample, even if a screen size is about 1 inch (2.56 cm in diagonal), adisplay device of VGA class (pixel numbers 640×480) can be realized.

[0115] However, since an area of a component, a width of a wiring, andthe like become small as the degree of integration of components becomeshigh, in order to keep the performance of a circuit, it becomesnecessary to lower the resistance of a polycrystalline silicon film usedfor a diffusion layer or a wiring. As one of methods for achieving thisobject, there is known a technique using self-aligned silicide (calledsalicide). This is such a method that a metal layer of titanium (Ti) orthe like is formed on a substrate, and silicide is formed by a heattreatment in a self-aligning manner in a region where silicon isexposed.

[0116] In this embodiment, an example in which an active matrix typedisplay device is fabricated by using the salicide technique will bedescribed with reference to FIGS. 18A to 20.

[0117] In FIG. 18A, a substrate 201 similar to that of the embodimentmode 1 is used, and a n-well region 202, and p-well regions 203 and 204are formed by one mask in a self-aligning manner. Further, a field oxidefilm 205 is formed. Then, a silicon oxide film 206 which becomes a gateinsulating film is formed by a thermal oxidation method. Gate electrodes207 to 209 are formed of polycrystalline silicon films in which ann-type impurity typified by phosphorus is added at a high concentration.

[0118] Next, as shown in FIGS. 18B and 18C, in order to form lightlydoped drain (LDD) regions in an n-channel FET and a p-channel FET,impurity elements which give an n-type and a p-type conductivity areadded using resist masks 210 and 213 as masks. This may be carried outby an ion doping method or an ion implantation method. Phosphorus (P) ision implanted to the n-channel FET, and boron (B) is ion implanted tothe p-channel FET. A dose amount is made 1×10¹³/cm². Ion implantation iscarried out by using the gate electrodes as masks, so that it ispossible to form, in a self-aligning manner, n-type impurity regions 211and 212 added with phosphorus (P) in regions where the n-channel FETsare to be formed, and a p-type impurity region 215 added with boron (B)in a region where the p-channel FET is to be formed.

[0119] Thereafter, an insulating film such as a silicon oxide film or asilicon nitride film is formed on the whole surface by a CVD method, andthis film is etched by anisotropic dry etching, so that side walls 216to 218 are formed at sides of the gate electrodes 207 to 209 as shown inFIG. 19A. Then, a resist mask 219 is formed, and boron (B) is ionimplanted to a region where the p-channel FET is to be formed, so that ap-type impurity region 220 is formed. The p-type impurity region 220 isformed to become deeper than the p-type impurity region 215 by makingthe acceleration voltage 50 to 100 keV.

[0120] As shown in FIG. 19B, after the resist mask 219 is removed, ametal layer 221 of Ti, Mo, Cr, or the like is formed on the wholesurface. Typically, Ti is used, and the layer is formed to a thicknessof 50 to 1000 nm on the whole surface by a sputtering method.Thereafter, a heat treatment is carried out at 600 to 800° C.,preferably 650 to 750° C. to form titanium silicide. Titanium silicideis formed in a self-aligning manner at a portion where the Ti film is incontact with silicon, and the Ti film remaining after the heat treatmentis selectively etched, so that titanium silicide layers 223 to 228 areformed on the gate electrodes formed of the polycrystalline siliconfilms and the p-type and n-type impurity regions as shown in FIG. 19C.However, in the titanium silicide film formed at a temperature of 800°C. or less, a high resistance phase is formed. When this film issubjected to a heat treatment at about 900° C. for about 5 to 120seconds, a low resistance phase is formed. Although this heat treatmentmay be carried out in a furnace annealing, a flash lamp annealing methodmay be used. By forming titanium silicide, it is possible to obtain asheet resistance of 2 to 4 Ω/□ for the gate electrode and the p-type orn-type impurity region.

[0121] Then, a resist mask 229 is formed in the region where thep-channel FET is to be formed, and arsenic having a dose amount of5×10¹⁵/cm² is implanted at an acceleration voltage of 50 to 120 keV tothe region of the n-channel FET by using the side walls and the gateelectrodes as masks, so that n-type impurity regions 230 and 231 areformed. The impurity regions are also formed to become deeper than then-type impurity regions 211 and 212.

[0122] As shown in FIG. 20, an interlayer insulating film 232 and aleveling film 233 made of phosphorus glass (PSG), boron glass (BSG), orboron phosphorus glass (BPSG) are formed. Thereafter, in order toactivate the ion implanted impurity element, a heat treatment is carriedout at 700 to 900° C. By this heat treatment, the leveling film 223 isreflowed, so that the flatness of the surface can be improved.

[0123] Then, contact holes are formed in the interlayer insulating film232 and the leveling film 233, and source or drain wirings 234 to 239are formed of Al films, laminate films of Ti and Al, or the like. Inthis state, when a heat treatment at 300 to 500° C., preferably 350 to450° C. is carried out in an atmosphere containing hydrogen,characteristics of the FET can be made more preferable.

[0124] A passivation film 240 to be formed thereon is formed of asilicon nitride film, a silicon oxide film, or a silicon oxynitridefilm, or the like with a thickness of about 50 to 200 nm, and further,an organic resin insulating layer 241 is formed to a thickness of 1 to 2μm. Moreover, a light shielding film 242 is formed of Al on the organicresin insulating layer 241, and its surface is oxidized by using theanodic oxidation method similarly to the embodiment mode 1 to form adielectric layer 243. Pixel electrodes 246 and 247 are formed thereon bya light reflective material typified by Al at a contact hole 254 throughopenings 244 and 245.

[0125] In the manner described above, on the single crystalline siliconsubstrate and by using the salicide technique, it is possible to form anactive matrix substrate in which a driver circuit portion including ap-channel FET 248 and an n-channel FET 249, and a pixel portionincluding an n-channel FET 250 and a storage capacitance 251 are formedon the same substrate. The storage capacitance is formed in the regionwhere the light shielding film 242, the dielectric film 243, and thepixel electrode 246 overlap with one another. The oxide film formed onthe surface of Al used as the light shielding film has high dielectricconstant, and by forming the film to a thickness of 50 to 100 nm, evenif the area of the pixel electrode per pixel is made small, capacitancenecessary for driving the pixel portion can be formed. For example, evenif an area of one pixel is made 400 μm², a capacitance of about 0.5 pFcan be formed.

[0126] The driver circuit portion is formed by using a CMOS circuit as abase, and it is possible to form a shift register circuit, a buffercircuit, a sampling circuit, a D/A converter, a latch circuit, or thelike. When such a circuit is constructed by an insulated gate FET usingsingle crystalline silicon as an active layer, a high speed operationbecomes possible and it is also possible to decrease consumed electricpower by making a driving voltage 3 to 5 V.

[0127] The p-type impurity region 215, and the n-type impurity regions211 and 212 become LDD regions, so that it is possible to preventdeterioration of the FET due to a hot carrier effect or the like.

[0128] Besides, by using the salicide technique, the resistance of thegate wiring can be lowered, and a problem of wiring delay can bereduced. Furthermore, since the resistance of the source or drain regionis lowered, the operation characteristics of the FET can be improved. Bythe effects as described above, the active matrix type display devicehaving a small size and high fineness can be realized.

[0129] The structure of the transistor explained in this embodiment ismerely one embodiment, and the present invention is not necessarilylimited to the fabricating steps and structure shown in FIGS. 18A to 20.The important point of the present invention is the structure of the FETformed on the single crystalline substrate and the storage capacitanceformed thereon through the organic resin layer.

[0130] [Embodiment 6]

[0131] In this embodiment, another embodiment of an active matrix typeEL display device will be described with reference to FIG. 21 and FIGS.22A and 22B. An active matrix substrate in which a driver circuitportion and a pixel portion are formed is fabricated in the same manneras the embodiment mode 1.

[0132] A n-well region 802 and p-well regions 803 to 805 are formed in aself-aligning manner in a substrate 801, and are separated by a fieldoxide film 806. Gate insulating films 810, 816, 822, and 828 are formedby a thermal oxidation method. Gate electrodes 811, 817, 823, and 829are formed of polycrystalline silicon layers 811 a, 817 a, 823 a, and829 a of polycrystalline silicon films formed to a thickness of 100 to300 nm by a CVD method, and silicide layers 811 b, 817 b, 823 b, and 829b formed to a thickness of 50 to 300 nm thereon. Reference numeral 849denotes a gate wiring.

[0133] As an impurity element which gives p-type conductivity, boron (B)having a dose amount of 1×10¹³ to 1×10¹⁴/cm² is added into a lightlydoped drain (LDD) region 807 of a p-channel FET 881. On the other hand,as an impurity element which gives n-type conductivity, phosphorus (P)or arsenic (As) is added at the same dose amount into LDD regions 813,819, and 825 of an n-channel FET 882, a switching FET 883 formed of ann-channel FET, and a current controlling FET 884. These LDD regions areformed in a self-aligning manner by an ion implantation method or iondoping method using the gate electrodes as masks.

[0134] Side walls 812, 818, 824, and 830 are formed in such a mannerthat after the LDD regions are formed, an insulating film such as asilicon oxide film or a silicon nitride film is formed on the wholesurface by a CVD method, this film is uniformly etched by anisotropicdry etching, and the insulating film is made to remain at the sides ofthe gate electrodes. A source region and a drain region of each FET areformed by using the side walls as masks. A source region 808 and a drainregion 809 in which boron (B) with a dose amount of 5×10¹⁴ to 1×10¹⁶/cm²has been ion implanted are formed in the p-channel FET 881. Sourceregions 814, 820, and 826, and drain regions 815, 821, and 827 in whicharsenic (As) with a dose amount of 5×10¹⁴ to 1×10¹⁶/cm² has been ionimplanted are formed in the n-channel FET 882, the switching FET 883formed of the n-channel FET, and the current controlling FET 884.

[0135] A first interlayer insulating film 831 is preferably a siliconoxide film or a silicon oxynitride film formed to a thickness of 100 to2000 nm by a plasma CVD method or a low pressure CVD method. Further, asecond interlayer insulating film 832 of phosphorus glass (PSG), boronglass (BSG), or boron phosphorus glass (BPSG) is formed thereon. Thesecond interlayer insulating film 832 is formed by a spin coating methodor a normal pressure CVD method, and by a treatment of thermalactivation serving also as a heat treatment of 700 to 900° C. carriedout after the formation, the second interlayer insulating film 832 isreflowed and the surface is flattened.

[0136] Source wirings 833, 835, 837, and 839, and drain wirings 834,836, 838, and 840 are formed after contact holes reaching the sourceregion and drain region of each FET are formed in the first interlayerinsulating film 831 and the leveling film 832, and it is appropriatethat Al normally used as a low resistance material is used. Besides, alaminate structure of Al and Ti may be used.

[0137] A passivation film 841 is formed of a silicon nitride film, asilicon oxide film, or a silicon oxynitride film by a plasma CVD method.Further, a third interlayer insulating film 842 is formed of an organicresin material with a thickness of 1 to 2 μm. A pixel electrode 843 isconnected to the drain wiring of the current controlling FET 884. Thepixel electrode is formed of a low resistance material typified by Al.

[0138] After the pixel electrode 843 is formed, a cathode layer 844containing metal with low work function is formed on the whole pixelelectrode. Since the film thickness is as thin as several nm, it is notapparent whether the layer is formed in a layer state or is scatteredlike islands. Thus, its contour is indicated by a dotted line.

[0139] As a material of the cathode layer containing metal having lowwork function, it is possible to use lithium fluoride (LiF), lithiumoxide (Li₂O), barium fluoride (BaF₂), barium oxide (BaO), calciumfluoride (CaF₂), calcium oxide (CaO), strontium oxide (SrO), or cesiumoxide (Cs₂O). Since these are insulative, even if they are formed into alayer state, a short (short circuit) between pixel electrodes is notcaused. Of course, although it is also possible to use a conventionalmaterial having conductivity, such as a MgAg electrode, as the cathodelayer, in order to prevent a short between the pixel electrodes, it isnecessary to selectively provide the cathode itself or to carry outpatterning.

[0140] An organic EL layer (electroluminescence layer) 845 is formed onthe cathode 844 containing the metal of the low work function. Althougha conventional material and a structure may be used for the organic ELlayer 845, in the present invention, a material capable of emittingwhite light is used. As the structure, only a light emitting layer toprovide a field of recombination may be made the organic EL layer, or asthe need arises, an electron injection layer, an electron transportlayer, a hole transport layer, an electron blocking layer, a holeblocking layer, or a hole injection layer may be laminated. In thepresent specification, the organic EL layer includes any layers whereinjection, transportation, or recombination of carriers is carried out.

[0141] As an organic EL material used for the organic EL layer 845, apolymer high molecular organic EL material is used. The organic EL layer845 is formed in such a manner that PVK (polyvinyl carbazole), Bu-PBD(2-(4′-tert-butylphenyl)-5-(4″-biphenyl)-1,3,4-oxadiazol), coumarin 6,DCM1 (4-dicyanomethylene-2-methyl-6-p-dimethylaminostvrvl-4H-pyran), TPB(tetraphenylbutadiene), or Nile red is dissolved in 1,2-dichloromethaneor chloroform, and is applied by a spin coating method. The number ofrevolutions is made about 500 to 1000 rpm, and revolution is made for 20to 60 seconds so that a uniform coating film is formed.

[0142] Of course, the organic EL material is subjected to refining(typically, dialysis) at least three times, preferably five times ormore, so that the concentration of contained sodium is made 0.1 ppm orless (preferably 0.01 ppm or less), and then, film formation is made. Bydoing so, the concentration of sodium contained in the organic EL layer845 shown in FIG. 21 becomes 0.1 ppm or less (preferably 0.01 ppm orless), and a volume resistance value becomes 1×10¹¹ to 1×10¹² ωcm(preferably 1×10¹² to 1×10¹³ ωcm).

[0143] A transparent conductive film as an anode layer 846 is formed onthe thus formed organic EL layer 845. As the transparent conductivefilm, it is possible to use a compound (called ITO) of indium oxide andtin oxide, a compound of indium oxide and zinc oxide, tin oxide (SnO₂),or zinc oxide (ZnO), or the like.

[0144] An insulating film as a passivation film 847 is formed on theanode layer 846. As the passivation film 847, it is preferable to use asilicon nitride film or a silicon oxynitride film (expressed by SiOxNy).

[0145]FIG. 22A is a top view of a pixel portion of an active matrix typeEL display device, and FIG. 22B is a view showing its circuit structure.Actually, a plurality of pixels are arranged in a matrix form so thatthe pixel portion (picture display portion) is formed. Incidentally, asectional view taken along the line A-A′ of FIG. 22A corresponds to asectional view of the pixel portion of FIG. 21. Thus, since commonnumerals are used in FIGS. 21 and 22A, reference may be suitably made toboth the drawings. Although the top view of FIG. 22A shows two pixels,both have the same structure. As shown in FIG. 22B, in an organic ELcomponent 885, two FETs are provided per pixel. Both are n-channel FETs,and function as the switching FET 883 and the current controlling FET884.

[0146] In the manner as described above, it is possible to form thedriver circuit including, as a base, the CMOS circuit made of thep-channel FET 881 and the n-channel FET 882, and the pixel portionincluding the switching FET 883 and the current controlling FET 884,which are formed of the n-channel FETs, on the single crystallinesilicon substrate. With respect to the driver circuit including the CMOScircuit as the base, for example, a shift register circuit, a buffercircuit, a sampling circuit, a D/A converter, a latch circuit, or thelike is formed using the CMOS circuit as the base. When such a circuitis formed of an insulated gate FET using single crystalline silicon asan active layer, a high speed operation becomes possible, and it is alsopossible to decrease consumed electric power by making a driving voltage3 to 5 V. Incidentally, the structure of the FET explained in thisembodiment is merely one embodiment, and the present invention is notnecessarily limited to the structure shown in FIG. 21.

[0147] Typical effects obtained in the present invention will beexplained below in brief.

[0148] In an active matrix substrate in which by means of FETs usingsingle crystalline semiconductor typified by single crystalline siliconas an active layer, a pixel portion and a driver circuit connected tothe pixel portion are provided on the same substrate, an organic resininsulating layer is formed on the FET, and a storage capacitance isformed of a light shielding film formed thereon, a dielectric layerformed to be in close contact with the light shielding film, and a pixelelectrode formed so that its part overlaps with the light shieldingfilm. Thus, it is possible to form a display device being capable ofoperating at high speed, with low consumed electric power and highreliability.

[0149] Such an active matrix substrate can be suitably used for a liquidcrystal display device using thresholdless antiferroelectric mixedliquid crystal.

[0150] In the above display device, by forming the dielectric layer tobe in close contact with the light shielding film by means of an anodicoxidation method, it becomes possible to form the excellent dielectriclayer without defects such as a pinhole. Moreover, by uniformly andthinly forming the dielectric layer having high dielectric constant bymeans of the anodic oxidation method, sufficient storage capacitance canbe secured even if a pixel pitch is shortened.

[0151] In the method of forming the dielectric layer to be in closecontact with the light shielding film provided on the organic resininsulating layer by means of the anodic oxidation method, when thecontrol pattern of formation voltage and formation current shown in FIG.13B is adopted, it is possible to form the dielectric layer in whichsoaking from the end does not occur. By forming the storage capacitancewith the thus fabricated dielectric layer, the display device havinghigh reliability can be realized.

What is claimed is:
 1. A semiconductor device comprising a pixel portionwith an insulated gate field effect transistor having at least an activelayer made of single crystalline semiconductor comprising silicon,wherein an organic resin insulating layer is formed over said insulatedgate field effect transistor, and wherein a storage capacitance isformed of a light shielding layer formed over said organic resininsulating layer, a dielectric layer formed to be in close contact withsaid light shielding layer, and a light reflecting electrode connectedto said insulated gate field effect transistor.
 2. A semiconductordevice comprising a pair of substrates and a liquid crystal interposedtherebetween, said semiconductor device comprising: an insulated gatefield effect transistor having at least an active layer made of singlecrystalline semiconductor comprising silicon over one of saidsubstrates, wherein an organic resin insulating layer is formed oversaid insulated gate field effect transistor, wherein a storagecapacitance is formed of a light shielding layer formed over saidorganic resin insulating layer, a dielectric layer formed to be in closecontact with said light shielding layer, and a light reflectingelectrode connected to said insulated gate field effect transistor, andwherein at least one light transmitting conductive film is formed overthe other of said substrates.
 3. A semiconductor device comprising aninsulated gate field effect transistor having at least an active layermade of single crystalline semiconductor comprising silicon, and anorganic EL component, wherein an organic resin insulating layer isformed over said insulated gate field effect transistor, and wherein astorage capacitance is formed of a light shielding layer formed oversaid organic resin insulating layer, a dielectric layer formed to be inclose contact with said light shielding layer, and a light reflectingelectrode connected to said insulated gate field effect transistor.
 4. Asemiconductor device according to any one of claims 1 to 3, wherein aninsulating layer made of an inorganic compound is formed between saidorganic resin insulating layer and said light shielding layer.
 5. Asemiconductor device according to any one of claims 1 to 3, wherein aninsulating layer made of an inorganic compound is formed on a surface ofsaid organic resin insulating layer at a side where said light shieldinglayer is formed.
 6. A semiconductor device according to claim 2, whereinsaid liquid crystal is thresholdless antiferroelectric mixed liquidcrystal.
 7. A semiconductor device according to any one of claims 1 to3, wherein said light shielding layer is made of at least one kind ofmaterial selected from the group consisting of aluminum, tantalum, andtitanium, and said dielectric layer is an oxide of said material.
 8. Asemiconductor device according to any one of claims 1 to 3, wherein saidsemiconductor device is one selected from the group consisting of aportable telephone, a video camera, a mobile computer, a goggle typedisplay, a projector, a portable book, a digital camera, and a DVDplayer.
 9. A method of fabricating a semiconductor device comprising apixel portion with an insulated gate field effect transistor having atleast an active layer made of single crystalline semiconductorcomprising silicon, said method comprising the steps of: forming anorganic resin layer over said insulated gate field effect transistor;forming a light shielding layer over said organic resin layer; forming adielectric layer to be in close contact with said light shielding layer;and forming a light reflecting electrode containing a region overlappingwith said light shielding layer through said dielectric layer.
 10. Amethod of fabricating a semiconductor device comprising a pair ofsubstrates and a liquid crystal interposed therebetween, said methodcomprising the steps of: forming an insulated gate field effecttransistor having at least an active layer made of single crystallinesemiconductor comprising silicon over one of said substrates; forming anorganic resin layer over said insulated gate field effect transistor:forming a light shielding layer over said organic resin layer; forming adielectric layer to be in close contact with said light shielding layer;forming a right reflecting electrode connected to said insulated gatefield effect transistor; and forming a light transmitting conductivefilm on the other of said substrates, wherein said light reflectingelectrode contains a region overlapping with said light shielding layerthrough said dielectric layer.
 11. A method of fabricating asemiconductor device comprising an insulated gate field effecttransistor having at least an active layer made of single crystallinesemiconductor comprising silicon, and an organic EL component, saidmethod comprising the steps of: forming an organic resin layer over saidinsulated gate field effect transistor; forming a light shielding layerover said organic resin layer; forming a dielectric layer to be in closecontact with said light shielding layer; and forming a light reflectingelectrode connected to said insulated gate field effect transistor,wherein said light reflecting electrode contains a region overlappingwith said light shielding layer through said dielectric layer.
 12. Amethod according to any one of claims 9 to 11, wherein an insulatinglayer made of an inorganic compound is formed between said organic resininsulating layer and said light shielding layer.
 13. A method accordingto any one of claims 9 to 11, wherein an insulating layer made of aninorganic compound is formed on a surface of said organic resininsulating layer at a side where said light shielding layer is formed.14. A method according to claim 10, wherein said liquid crystal isthresholdless antiferroelectric mixed liquid crystal.
 15. A methodaccording to any one of claims 9 to 11, wherein said light shieldinglayer is made of at least one kind of material selected from the groupconsisting of aluminum, tantalum, and titanium, and said dielectriclayer is an oxide of said material.
 16. A method according to claim 15,wherein said dielectric layer is formed by an anodic oxidation method.17. A method according to any one of claims 9 to 11, wherein saidsemiconductor device is one selected from the group consisting of aportable telephone, a video camera, a mobile computer, a goggle typedisplay, a projector, a portable book, a digital camera, and a DVDplayer.